AWIO20 FMEE 111156
BULLETIN FOR CYCLONIC ACTIVITY AND SIGNIFICANT TROPICAL WEATHER IN
THE SOUTHWEST
INDIAN OCEAN
DATE: 2011/04/11 AT 1200 UTC
PART 1 :
WARNING SUMMARY : Nil.
PART 2 :
TROPICAL WEATHER DISCUSSION
:
Convective activity over the basin is mainly associated with a
baroclinic low pressure area that formed 48 hours ago off the
southeastern coast of Madagascar.
Surface obs, satellite imagery and ASCAT data of 0640Z suggest that
a low is deepening at about 40 NM to the Southsoutheast of
Fort-Dauphin (Madagascar). It is located at 10Z near 25.8S and
47.3E. Thunderstorm activity is maintaining close to the center
mainly in the southern and western sectors. MSLP is estimated at
1007 hPa with pressure at nearby stations showing strong fall (-6.7
hPa in 24hrs at Fort-Dauphin and -5.7 hPa in 24 hrs at Farafangana
at 09Z). As suggested by ASCAT data and available surface obs, wind
structure is very asymetric currently with 10/20 kt winds in the
northern semi-circle and near gales force to locally gales force
winds in the southern semi-circle mainly due to gradient effect.
The system is currently within a baroclinic environment (cold upper
level low) with a lower than usual dynamical tropopause. However
given that deep convection is maintaining close to the center, that
the system evolves over warm waters (26-27C SST) and that the shear
is expected to be rather low under the upper level low, it appears
likely that this system could gain some tropical characteristics
(tropical transition) within the next few days ... if it does not
make landfall rapidly over the southeastern coast of Madagascar ...
Located to the Northeast of this low pressure area, a convergence
line associated with severe thunderstorm is axed along 20S/51E -
24S/54E between the Mascaregnes islands and Madagascar.
For the next 72 hours, the potential for the system located south
of Madagascar to gain some tropical characteristics is poor to
fair.

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